1. Field of the Invention
The present invention relates to a semiconductor laser apparatus capable of emitting a plurality of light beams having different wavelengths and a fabrication method thereof.
2. Description of the Background Art
Conventionally, CD (Compact Disk)/CD-R (Compact Disk-Recordable) drives have employed semiconductor laser devices which emit infrared beams of light with a wavelength of approximately 780 nm (infrared semiconductor laser devices) as light sources. Conventional DVD (Digital Versatile Disk) drives, on the other hand, have employed semiconductor laser devices which emit red beams of light with a wavelength of approximately 650 nm (red semiconductor laser devices) as light sources.
Meanwhile, the development of DVDs is recently progressing which can be recorded and played back using blue-violet beams of light with a wavelength of approximately 405 nm. In order to record and play back such DVDs, the development of DVD drives using semiconductor laser devices which emit blue-violet beams of light with a wavelength of approximately 405 nm (blue-violet semiconductor laser devices) is simultaneously progressing. Such DVD drives require compatibility with conventional CDs/CD-Rs and DVDs.
In this case, compatibility with conventional CDs, DVDs, and new DVDs is achieved using a method of providing a DVD drive with a plurality of optical pickup apparatuses which emit infrared, red, and blue-violet beams, respectively, or a method of providing an infrared semiconductor laser device, red semiconductor laser device, and blue-violet semiconductor laser device in one optical pickup apparatus. The above-described methods, however, result in an increase in parts count, thus making it difficult to make a smaller, simpler, and lower-cost DVD drive.
In order to prevent such an increase in the parts counts, semiconductor laser devices each comprised of an infrared semiconductor laser device and a red semiconductor laser device integrated into a single chip are in practical use.
The infrared semiconductor laser device and red semiconductor laser device, which are both formed on a GaAs substrate, can be formed into a single chip. The blue-violet semiconductor laser device, however, is not formed on a GaAs substrate, which makes it very difficult to be integrated into a single chip together with the infrared and red semiconductor laser devices.
JP 2001-230502 A suggests a light emitting device to overcome such difficulties. This light emitting device is obtained as follows: an infrared semiconductor laser device and a red semiconductor laser device are formed on the same chip to fabricate a monolithic red/infrared semiconductor laser device; simultaneously, a blue-violet semiconductor laser device is formed on a different chip; after this, the chip of the blue-violet semiconductor laser device and the chip of the monolithic red/infrared semiconductor laser device are laminated.
In the above-described light emitting device, however, the red semiconductor laser device and infrared semiconductor laser device are formed on a common n-type substrate due to the structure of the monolithic red/infrared semiconductor laser device. The p-side electrodes of the infrared semiconductor laser device and red semiconductor laser device are mounted on the n-type substrate of the blue-violet semiconductor laser device. Such a structure results in limited space for connecting a wire that is attached to each electrode. This makes wiring of the light emitting device complicated.